This project continues the examination of the hormonal and behavioral bases for successful reproduction in the cotton-top tamarin. We have developed non-stressful techniques for collecting urine samples which can then be analyzed for hormones. We will develop assays for urinary progesterone and testosterone to supplement the assays for estrogens and luteinizing hormone already developed. These hormonal assays will then be used in the following projects: (1) Determination of hormonal levels through ovulation and pregnancy: Daily urine samples will be collected from six females from partuition through the subsequent partuition and pregnancy. This will provide the first complete daily hormonal characterization of an entire reproductive cycle in a tamarin and is possible due to the nonstressful collecting technique. Preliminary results indicate that females experience only one ovulation post-partum before becoming pregnant again, and that gestation is much longer in these animals than had previously been suspected. (2) Social contraception: Female tamarins in a subordinate role fail to ovulate in the presence of a more dominant female, yet quickly ovulate when removed from a family group and placed with a mate of their own. Hormonal and behavioral measurements will be made of females in family groups and then after removal from the group. Following pairing with a mate, half of the females will receive daily transfers of scent marking from their mother's cages to determine if maternal scent marking is the cause of the social contraception. (3) Behavioral estrus: Several writers have speculated that monogamous females use concealed ovulation as a tactic to deceive males to stay with them. It has proven difficult to find obvious signs of estrus in marmosets and tamarins, but not study to date has made simultaneous behavioral and hormonal measurements. We propose to take behavioral observations of females for several ovulatory cycles while taking daily urine samples on those same animals in order to determine if there is a behavioral correlate. Such a correlate would be of great use in the captive breeding of these animals. (4) Aging: Little is known of the hormonal and behavioral responses to aging in monogamous primates. We have some quite old tamarins and will examine their hormonal status in a longitudinal study. (5) Male hormones and behavior: No work has been done on male hormonal maturation in tamarins, yet males also show an inhibition of reproduction while with their fathers. We will study hormonal and behavior reproductive maturation in male tamarins.